6.8

External capacitors and application suggestions

Input and output capacitors are mandatory to reduce the transient effects of stray inductances which may be

present on the input and output power paths. In fact, when the STEF512SRI interrupts the current flow, input

inductance generates a positive voltage spike on the input, and output inductance generates a negative voltage

spike on the output. To reduce the effects of such transients, a CIN capacitor of at least 1 μF (including derating

effects) must be connected between the input pin and GND and located as close as possible to the device.

For the same reason, a COUT capacitor of at least 10 μF must be connected at the output port.

When the device is connected to the power supplies by means of long wires, whose inductance is higher than 1

µH, the input capacitor should be increased.

It is suggested to provide for additional protections and methods for addressing these transients, such as:

•

Minimizing inductance of the input and output tracks

•

TVS diodes on the input to absorb inductive spikes

•

Schottky diode on the output to absorb negative spikes

•

A combination of ceramic and electrolytic capacitors on the input and output.

STEF512SRI

External capacitors and application suggestions

DS14138 - Rev 1

page 12/28